1. Field of the Invention
The present invention relates to an insert. More specifically, the present invention relates to inserts for installation into components made from plastics materials.
2. Description of the Related Art
Metal inserts are commonly used for the attachment of components constructed from plastics materials. Plastics materials are not particularly well suited to the formation of mechanical joining features such as threads as they have relatively low stiffness and strength compared to metals. As such, it is common practice to permanently install metal inserts into plastic components to provide mechanical joining features. These metal inserts have internal mechanical joining features such as threads.
Inserts are commonly cylindrical in form and comprise features on their external surface to inhibit movement between the insert and the plastic component (anti-movement features). These may be circumferential features to provide pull-out resistance or axial features for torque resistance. Such features may have both circumferential and axial parts, such as knurls.
Metal inserts of the type described above are used in many applications such as vehicle assembly—e.g. interior trim.
Such metal inserts are commonly installed into the plastic components by locally heating the insert and/or the plastics material and forcing the insert into the component. The semi-fluid plastics material then flows around locking features of the insert and cools to provide a permanent mechanical bond between the component and the insert. Another known method is to vibrate the insert at a high frequency to create frictional heating at the insert-plastic boundary. This heating causes the plastics material to melt and flow around the insert external features before cooling and solidifying to form a bond.
Heat is applied to the insert prior to installation to heat the insert to a temperature above the softening point temperature of the plastics material. As the insert is installed, the plastic material draws heat from the insert and softens to flow around the insert external profile. The amount of energy required to complete the installation is therefore influenced by the time taken to complete the installation process. The time taken to install the insert is controlled by the insert design and the distance the insert travels during the insertion process.
A problem with such installation techniques is that the distance the insert must travel is generally equal to the length of the insert, and as such a significant amount of energy needs to be used to heat the insert in order to install it. Much of the insert is not contacting the plastics material during installation and as such the heat may be dissipated to the surrounding environment.
Alternatively, ultrasonic energy may be used to heat the insert and surrounding plastics material during installation. Therefore ultrasonic energy must be supplied during the entire installation. As such, as the entire insert must be vibrated for the entire time it takes to fully install the insert. This is not energy efficient as, particularly during the initial stages of installation, much of the length of the insert is not contacting the plastics material.
It is an aim of the present invention to overcome or at least mitigate the above problem.